Direct Tension Recording From Smooth Muscle of Resistance Vessels From Various Organs

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67115/2/10.1177_000331976101201009.pd

Analytic Structure of Three-Mass Triangle Coefficients

``Three-mass triangles'' are a class of integral functions appearing in one-loop gauge theory amplitudes. We discuss how the complex analytic properties and singularity structures of these amplitudes can be combined with generalised unitarity techniques to produce compact expressions for three-mass triangle coefficients. We present formulae for the N=1 contributions to the n-point NMHV amplitude.Comment: 22 pages; v3: NMHV n=point expression added. 7 point expression remove

Characterization of the rat basilar artery in vitro

Segments of the rat basilar artery were examined in vitro for their mechanical responsiveness to a variety of vasoactive substances. Serotonin was the most potent agonist while norepinephrine elicited a dose-dependent relaxation. The findings lend support to the concept that there exists a marked heterogeneity amongst species in cerebrovascular responsiveness.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42737/1/18_2005_Article_BF01959732.pd

Role of electrolytes in the contractile machinery of vascular smooth muscle

The following observations of the effect of imposed alteration in electrolyte composition on the contractility of vascular smooth muscle emphasized the complexity of the processes involved: 1. 1. Studies based on the relation of changes in mechanical performance in response to changes in intracellular potassium (Ki) and in the Ki/Ko ratio constitute strong evidence that the potassium ion can influence vascular smooth muscle response both through its gradient across the cell membrane and by direct action of its intracellular concentration.2. 2. While an increase in potassium concentration in the bath causes only an increase in the magnitude of response of smooth muscle from large conduit vessels, the effect of an increase in potassium concentration on the response of resistance vessels is usually biphasic, small increases depressing and larger increases potentiating the response. These observations constitute further evidence of at least a dual action of potassium.3. 3. Six steroids were compared as to their ability to produce a potentiation of an epinephrine response. The relative potentiating action bore no relation to their known physiologic effects or to their ability to produce hypertension.4. 4. A decrease in sodium concentration in the bath causes an increase in the responsiveness of smooth muscle from both conduit and resistance vessels.5. 5. A decrease in calcium in the bath results in a decrease in the responsiveness of smooth muscle from both of these vessels.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32349/1/0000420.pd

The No-Triangle Hypothesis for N=8 Supergravity

We study the perturbative expansion of N=8 supergravity in four dimensions from the viewpoint of the ``no-triangle'' hypothesis, which states that one-loop graviton amplitudes in N=8 supergravity only contain scalar box integral functions. Our computations constitute a direct proof at six-points and support the no-triangle conjecture for seven-point amplitudes and beyond.Comment: 43page

Intrinsic difference in erythrocyte membrane in spontaneously hypertensive rats characterized by Na + and K + fluxes

The goad of this study was to determine whether the elevated flux of sodium and potassium through the erythrocyte membrane of spontaneously hypertensive rats (SHR) is due to an intrinsic difference in the cell membrane or to a humoral factor present in the plasma. Isolated and washed erythrocytes from SHR and normotensive Wistar Kyoto (WKy) and Sprague-Dawley (SD) rats, were incubated in 1) a physiological salt solution, 2) WKy or SD plasma and 3) SHR plasma. Incubations were performed at 4°C for 23 h. Erythrocytes from SHR incubated in physiological salt solution had significantly greater Na + and K + fluxes than those from normotensive WKy and SD rats ( P WKy>SHR. Erythrocyte K + efflux was not altered by plasma. We conclude that the elevated flux of Na + and K + in SHR erythrocytes is due to an intrinsic difference in the cell membrane. The greater Na + influx in plasma from any strain of rats is not correlated with the blood pressure of the rat. The lesser increase in Na + influx in crythrocytes incubated in plasma from SHR masks the greater intrinsic membrane permeability in the SHR erythrocyte when Na + fluxes are studied in whole blood. The elevated flux of Na + and K + through the erythrocyte membrane of SHR may reflect a general membrane defect that underlies the pathogenesis of elevated arterial pressure.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47450/1/424_2004_Article_BF00652525.pd

Potassium-induced vascular relaxation in two kidney-one clip, renal hypertensive rats

This study was designed to characterize potassium-induced relaxation in vascular smooth muscle in two kidneyone clip (2K-1C), renal hypertensive rats. Potassium-induced relaxation was evaluated in the isolated tail artery and in the isolated pump perfused renal vasculature. Both preparations relaxed in response to potassium after contraction induced by norepinephrine in potassium-free solution. Arterial preparations from hypertensive rats showed greater relaxation than did those from normotensive rats. Potassium-induced relaxation in tail arteries from hypertensive rats was more sensitive to ouabain inhibition than those from normotensive rats; the renal vasculature of hypertensive rats did not differ from controls with respect to ouabain sensitivity. Relaxation in response to potassium in isolated tail artery segments varied with the: 1. length of incubation in potassium-free solution; 2. concentration of added potassium; and 3. concentration of norepinephrine added during the potassium-free interval. The amplitude of potassium relaxation is believed to be a functional measure of the electrogenic sodium pump. These experiments support the hypothesis that vascular smooth muscle from 2K-1C renal hypertensive rats has increased electrogenic sodium pump activity, in vitro.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47449/1/424_2004_Article_BF00584701.pd

Possible role of sodium-calcium pumps in tension development of vascular smooth muscle,

Observations were made on the tension development by helical strips of vascular smooth muscle from rabbit aorta and mesenteric artery. Based on the possibility that the pump which moves calcium into the cell coupled with sodium efflux, recently described for squid axon (1), exists also in vascular smooth muscle, studies were designed to evaluate changes in its activity in this muscle. Sodium competes with calcium for the carrier at the cell surface, hence the pump moves calcium into the cell more rapidly in a sodium-free medium. The strips developed more tension in a sodium-free solution, as if more ionized calcium were being delivered to the cell. Ouabain is known to block the sodium-potassium pump, thereby permitting an increase in sodium concentration inside the cell; this in turn will aceclerate the sodium-calcium pump. Ouabain potentiated the contractile responses of these muscles, suggesting that a higher concentration of ionized calcium is reaching the contractile protein.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32889/1/0000268.pd